LONDON, March 22 (Reuters) - Twitter CEO Jack Dorsey sold his first tweet as a non-fungible token (NFT) for just over US$2.9 million dollars on Monday (Mar 22).

NFT is a kind of unique digital asset that has exploded in popularity so far in 2021.

Each NFT has its own blockchain-based digital signature, which serves as a public ledger, allowing anyone to verify the asset's authenticity and ownership.

The tweet - "just setting up my twttr" - was Dorsey's first tweet, made on March 21, 2006.

The NFT was sold via auction on a platform called Valuables, which is owned by the US-based company Cent.

It was bought using the cryptocurrency Ether, for 1630.5825601 ETH, which was worth US$2,915,835.47 at the time of sale, Cameron Hejazi, the CEO and co-founder of Cent confirmed.

Cent confirmed the buyer is Sina Estavi. Estavi's Twitter profile, @sinaEstavi, says he is based in Malaysia and is CEO of the blockchain company Bridge Oracle.

Estavi told Reuters he was "thankful" when asked for comment about the purchase.

On Mar 6, Dorsey, who is a bitcoin enthusiast, tweeted a link to the website where the NFT was listed for sale. He then said in another tweet on Mar 9 that he would convert the proceeds from the auction into bitcoin and donate them to people impacted by COVID-19 in Africa.

Dorsey receives 95 per cent of the proceeds of the primary sale, while Cent receives 5 per cent.

Cent CEO Cameron Hejazi said that his platform allows people to show support for a tweet that goes beyond the current options to like, comment and retweet.

"These assets might go up in value, they might go down in value, but what will stay is the ledger and the history of 'I purchased this from you at this moment in time' and that's going to be in both the buyer, the seller and the public spectators' memory," Hejazi said, adding that this was "inherently valuable."